ul,
li {
    list-style: none;
    margin: 0;
    padding: 0;
}

body {
    background-color: #6e6e6e;
}

div {
    /* 所有元素禁止选中文本 */
    user-select: none;
}

.cal-btn {
    width: 82px;
    height: 82px;
    line-height: 82px;
    font-size: 16px;
    text-align: center;
    margin: 100px auto;
    background-color: #1E1E1E;
    color: white;
    border-radius: 50%;
}

.cal-btn:hover {
    cursor: pointer;
    background-color: #323233;
    box-shadow: 3px 3px 10px rgba(0, 0, 0, .8);
}

.bg {
    display: none;
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    background-color: rgba(0, 0, 0, .4);
}

.tips {
    position: fixed;
    top: 250px;
    left: 50px;
    display: none;
    height: 520px;
    width: 300px;
    background-color: #000;
    border-radius: 44px;
    box-shadow: 4px 4px 15px rgba(0, 0, 0, .8);
    overflow: hidden;
}

.tips-border {
    /* 每个按钮的边框盒子 */
    position: relative;
    width: 104px;
    height: 104px;
    background-color: #000;
}

.tips-btn {
    /* 每个圆形按钮 */
    width: 88px;
    height: 88px;
    border-radius: 50%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #fff;
    font-size: 40px;
    text-align: center;
    line-height: 88px;
    background-color: #333;
}

.explain {
    float: right;
    height: 104px;
    width: 150px;
    color: #fff;
    margin-right: 20px;
    font-size: 40px;
    text-align: left;
    line-height: 104px;
}

.delete-one {
    width: 300px;
    height: 104px;
    color: #fff;
    font-size: 40px;
    text-align: center;
    /* background-color: pink; */
    line-height: 104px;
}

.Calculator {
    /* 计算器大盒子 */
    position: fixed;
    z-index: 99;
    top: 100px;
    left: 400px;
    display: none;
    width: 416px;
    height: 664px;
    background-color: #000;
    border-radius: 44px;
    overflow: hidden;
    box-shadow: 4px 4px 15px rgba(0, 0, 0, .8);
}

.header {
    /* 头部拖动栏 */
    position: relative;
    width: 100%;
    height: 40px;
    background-color: #333;
}

.header:hover {
    cursor: move;
}

.close {
    /* 拖动栏中的关闭按钮 */
    position: absolute;
    right: 30px;
    top: 50%;
    margin-top: -15px;
    width: 30px;
    height: 30px;
    text-align: center;
    font-size: 25px;
    line-height: 30px;
    border-radius: 50%;
    background-color: red;
    box-shadow: 0 0 5px rgba(0, 0, 0, .7) inset;
}

.close:hover {
    background-color: #FF9F18;
    cursor: pointer;
}

.displayBox {
    width: 100%;
    height: 104px;
    background-color: #000;
}

.display {
    /* 输入的数字显示区域 */
    width: 96%;
    height: 104px;
    font-size: 60px;
    color: #fff;
    line-height: 104px;
    text-align: right;
}

.btns {
    /* 按钮大盒子 */
    display: flex;
    flex-wrap: wrap;
}

.border {
    /* 每个按钮的边框盒子 */
    position: relative;
    width: 104px;
    height: 104px;
    background-color: #000;
}

.btn {
    /* 每个圆形按钮 */
    width: 88px;
    height: 88px;
    border-radius: 50%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #fff;
    font-size: 40px;
    text-align: center;
    line-height: 88px;
    background-color: #333;
}

.hidden {
    visibility: hidden;
}

.zero-border {
    /* 按钮0的边框 */
    position: absolute;
    bottom: 0;
    left: 0;
    width: 208px;
    height: 104px;
    background-color: #000;
}

.zero-btn {
    /* 按钮0 */
    width: 192px;
    height: 88px;
    border-radius: 44px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #fff;
    font-size: 40px;
    text-align: center;
    /* text-align: left; */
    /* padding-left: 50px; */
    line-height: 88px;
    background-color: #333;
}

.gray {
    /* 灰色的按钮 */
    background-color: #A6A6A6;
    color: #000;
    font-weight: 700;
    font-size: 34px;
}

.yellow {
    /* 黄色的按钮 */
    background-color: #FF9F18;
    font-weight: 700;
    font-size: 44px;
}

.zero-btn:hover,
.btn:hover {
    background-color: #29E3F5;
}

.zero-btn:active,
.btn:active {
    background-color: #00717C;
}